At first, the Japanese didn't have surnames, but later the nobles had surnames, and only later did the people begin to have surnames. At first, when they were inexperienced, everyone took it at random. The pig raiser's surname was pig rice. Those who kill pigs are surnamed pig heads; The name of the rice shop is Mi Wu; Open an oil shop, surnamed Wei Xiang; Engaged in the romantic industry, surnamed the prostitute man; The famous Japanese ninja is called Hattori Shimada Hanzo, whose ancestors were weavers. There is always a generation of ancestors named Hattori who spin, weave and make clothes. There is a first authority on Japanese communication. His surname is my grandson.
surnames are so casual, and that name is even more casual. They don't take it seriously, so don't take it seriously. There is no naming method, there is no such rule. What they came up with, we can't think of it even if we want to break our brains.
very casual, of course, it may also mean sorting by seniority.